Knowledge is uncountable. – Karsten (2018)
Grammatically, knowledge is uncountable. Physiologically, it is also uncountable. Simply because there are way too much “knowledge” that exists, not to mention those that will eventually come to reality.
There has been an interesting trend amongst juveniles in Hong Kong. They publicly post on forums or social media and asks whether people would like to “exchange knowledge”. The idea behind this is that basically everyone knows something other does not. Usually there are skills or knowledge that are uncommon, to learn that you usually need to do researches or simply pay a tutor to teach you.
I’ve accepted to “exchange” my understanding to various types of chess(chess, chinese chess, go, etc.) with a girl of same age recently. In return she will teach me French(at the moment I know only bonjour.). I am thrilled as I have never learnt foreign languages except English, I tried to learn Latin but I soon found it difficult, then I gave it up.
Teaching others continously renew your understanding to what you are teaching. This could be understanded as some sort of “revision”. Eventually the knowledge will be converted to long term memory as your brain values it “important”, because you frequently utilize it.
Globally there are apps on iOS and android that enables strangers to teach each other languages they don’t yet know and are interested in. Personally I love this idea. You get to learn a language from a native speaker almost for free(surely you have to purchase a subscription for the app to learn more), and in exchange you get to teach others! This is satisfying as you learn and help at the same time. I don’t use them, because I don’t really have the motivation to do so(I haven’t even read the Latin textbook I’ve downloaded from Wikibooks).